Fishers’ knowledge indicates that collective benefits outweigh the individual costs of coexisting with dolphins

Abstract

Understanding interactions between small-scale fishers and endangered dolphins is crucial for informing coexistence strategies. We investigated the perceptions and encounters of 123 Amazonian fishers in the Tapajós River (Brazil) with two endangered freshwater dolphins, Sotalia fluviatilis and Inia geoffrensis. Furthermore, 51 fishers self-documented 2,013 fish landings over one year. All interviewed fishers reported regular encounters with dolphins during fishing activities, with landings and interviews showing a partial overlap in fish species caught by fishers and cited as consumed by dolphins. Fishers highlighted that only I. geoffrensis disrupts fishing activities, causing gillnet damage and stealing fish from nets. To avoid interaction, fishers refrain from fishing an average of 3.7 times per month, potentially leading to 14.8 to 18.5 % decrease in total fish harvest. Economic losses were reported by 63 fishers, totaling an estimated US$ 50.3 ± 30.1 per month per fisher, which is equivalent to three days of fishing income. The estimated bycatch of dolphins was 10 per year across the studied area (71 % from I. geoffrensis). While 86 fishers considered dolphins beneficial, 62 viewed them as harmful. Fishers who fish more frequently are more likely to consider dolphins “good”. The results revealed dolphins’ positive contribution to fisheries by reducing efforts and safeguarding fish, while causing harm through gillnet damage. Negative perceptions are linked to individual economic losses, while positive perceptions stem from perceived collective benefits. By emphasizing dolphins’ collective advantages in riverine communities, they can be a flagship species for conservation, leveraging their appeal and function as umbrella species for maintaining ecosystem functions, such as healthy fish stocks.